refactor: modularize backend security and observability

backend/utils/device.js

@@ -0,0 +1,68 @@
+function normalizeClientIp(rawIp) {
+  const ip = String(rawIp || '').trim();
+  if (!ip) return '';
+  if (ip.startsWith('::ffff:')) return ip.slice(7);
+  return ip === '::1' ? '127.0.0.1' : ip;
+}
+
+function detectDeviceTypeFromUserAgent(userAgent = '') {
+  const mobilePattern = /(Mobile|Android|iPhone|iPad|iPod|Windows Phone|HarmonyOS|Mobi)/i;
+  return mobilePattern.test(String(userAgent || '')) ? 'mobile' : 'desktop';
+}
+
+function inferPlatformFromUserAgent(userAgent = '') {
+  const value = String(userAgent || '');
+  if (!value) return '未知平台';
+  if (/windows/i.test(value)) return 'Windows';
+  if (/macintosh|mac os x/i.test(value)) return 'macOS';
+  if (/android/i.test(value)) return 'Android';
+  if (/iphone|ipad|ios/i.test(value)) return 'iOS';
+  if (/linux/i.test(value)) return 'Linux';
+  return '未知平台';
+}
+
+function normalizeClientType(value = '') {
+  const normalized = String(value || '').trim().toLowerCase();
+  return ['web', 'desktop', 'mobile', 'api'].includes(normalized) ? normalized : '';
+}
+
+function resolveClientType(clientType, userAgent = '') {
+  const normalized = normalizeClientType(clientType);
+  if (normalized) return normalized;
+
+  const userAgentValue = String(userAgent || '').toLowerCase();
+  if (
+    userAgentValue.includes('tauri')
+    || userAgentValue.includes('electron')
+    || userAgentValue.includes('wanwan-cloud-desktop')
+    || userAgentValue.includes('玩玩云')
+  ) {
+    return 'desktop';
+  }
+  return detectDeviceTypeFromUserAgent(userAgentValue) === 'mobile' ? 'mobile' : 'web';
+}
+
+function sanitizeDeviceText(value, maxLength = 120) {
+  return typeof value === 'string' ? value.trim().slice(0, maxLength) : '';
+}
+
+function buildDeviceName({ clientType, deviceName, platform }) {
+  const preferred = sanitizeDeviceText(deviceName, 120);
+  if (preferred) return preferred;
+
+  const platformText = sanitizeDeviceText(platform, 80) || '未知平台';
+  if (clientType === 'desktop') return `桌面客户端 · ${platformText}`;
+  if (clientType === 'mobile') return `移动端浏览器 · ${platformText}`;
+  if (clientType === 'api') return `API 客户端 · ${platformText}`;
+  return `网页端浏览器 · ${platformText}`;
+}
+
+module.exports = {
+  buildDeviceName,
+  detectDeviceTypeFromUserAgent,
+  inferPlatformFromUserAgent,
+  normalizeClientIp,
+  normalizeClientType,
+  resolveClientType,
+  sanitizeDeviceText
+};